The present invention is concerned with devices for selectively separating trash particles from textile fibers and for selectively separating/sorting shorter fibers from longer fibers, i.e. converting fiber properties from one category to other categories.
The fibers delivered to textile mills, as raw materials for processing, are usually a mixture of dust, impurities and fibers having varying lengths ranging from long fibers to short fibers. During the initial processing steps of opening, cleaning, and carding, many of the original longer fibers are broken, producing even more short fibers. It is well known that the presence of the shorter fibers and tiny pulverized trash particles seriously and adversely affects the ability to spin "high quality" yarns. For this reason, high quality fine-count cotton mills usually sort their fibers by length before the spinning process. It is almost universally agreed that, today, the most effective way to length-sort fibers on a production scale is by use of reciprocating or oscillating combing machines. Their combs also strip out many of the tiny pulverized trash particles. Conventional combers are the most complicated machines used in any of the spinning processes. Owing in part to their high capital costs, high complexity, and high maintenance costs, and the fact that several extra fiber paralleling processing steps must be added in order for conventional combers to even work satisfactorily, adds from 18% to 40% to the processing costs for "combed" yarns, as compared to plain "carded" yarns. However, in view of the many yarn quality advantages provided by length-sorting, most cotton mills would comb or length-sort today were it not for the tremendous costs involved. There has been a long standing and urgent need for a better way to length-sort and purify textile fibers.
Proof of this long standing and urgent need is found in the fact that there have been a tremendous number of prior art attempts to address this critical problem. For example, U.S. Pat. Nos. 5,365,640, 5,333,358, 4,631,781, 4,471,607, 5,111,551, 3,737,952 4,135,275, 5,241,726, 3,579,744 and 4,064,598, and Gunter Cooke publication "The G.C. 600M-3Ace" 10-1968 are representative of just a few of the many, many past attempts to use toothed rolls or cylinders, rotating at high speeds, in order to create sufficient centrifugal forces to sling the undesirable fibers and other impurities from the desirable fibers carried by the teeth. Some of these devices have added one or more sharp edged devices ("mote knives") which are disposed adjacent to the periphery of the spinning toothed rolls. Mote knives act to enhance the separation of the impurities from the fibers by inertially popping, or stripping, the tightly bound impurities off of the fibers restrained on the moving teeth. Some of these devices have also incorporated suction boxes, suction hoods, or suction slots which are disposed near to the periphery of the spinning toothed rolls in order to further enhance the purification operation by capturing the impurities as they are stripped from the fibers under process, and conveying them away by air currents. This ensures that the dislodged impurities do not become re-entrapped in the fibers from which they were just extracted.
At this point, it is very important to remember that the adhesion/entanglement forces between the longer desirable fibers and the shorter less desirable fibers and the pulverized trash particles are extremely high--because many of the shorter fibers are actually immature fibers having thin underdeveloped cellular walls and their ribbon-like shapes causes them to wrap tightly and repeatedly around the longer fibers (which are also curled ribbons). Also, viewed under a microscope, the small pulverized trash particles usually look like miniature cockleburrs, having a great affinity to being repeatedly wrapped by the curly and rough surfaces of the longer fiber ribbons. Therefore, a great deal of mechanical work must be done in order to overcome these high entanglement forces. Consequently, the prior art that relies solely on high centrifugal forces to effect purification, is most suitable for extracting only large trash particles. The prior art that relies on a combination of centrifugal forces and "mote knives" to effect purification can extract both large particles and some of the finer particles and shorter fibers. It is well known, however, that when the centrifugal forces rise to the level that small particles and short fibers start to become effectively stripped off of the longer fibers, then the high contact velocity of the fibers striking the sharp "mote knife" edges causes fractures and bruising of the longer desirable fibers. Needless to say, breaking good fibers in order to remove impurities and some shorter fibers is not a very good solution to the problem.
In order to treat the fibers less violently, there also have been a tremendous number of prior art attempts to purify fibers via the use of porous defined wall screens. For example, U.S. Pat. Nos. 4,827,574, 5,327,617, 5,432,980, 4,809,404, 5,031,280, 3,815,178, 4,274,178, 5,303,455, 2,987,779, and 3,145,428 are representative of just a few of the many screen configurations that have been used in a non-impact manner. In addition, U.S. Pat. Nos. 4,519,114, 1,026,432, 1,593,965, 1,458,870, 1,605,196, 1,942,368, 2,025,701, and 5,150,502 are representative of just a few of the many applications where screens have been used either as "condensers", or as "impact" cleaners.
It is well known in the textile arts that whenever fibers are either placed on, or slammed against, porous defined wall screens and air currents flow through the fibrous mass, then a certain small fraction of the impurities contained therein may become dislodged and carried away in the air flowing through the apertures of the screens. However, it is also known that the fraction of impurities dislodged, compared to the total impurities burden present, is woefully small, and screens used in this manner are best suited for "de-dusting" purposes, rather than for removing short fibers longer than about 1/8 inch (4 mm) or jagged small trash particles. There are a number of reasons for this purification inefficiency; one of which is the phenomenon called "felting." "Felting" occurs primarily because the free ends of highly opened fibers poke through the apertures of the screens and tend to get hooked and twisted together, and adjacent non-hooked fibers cling to these because of the natural affinity of curled fibers to interlock tightly with one another. Whenever fibers "felt" on a screen they build a filtering media that traps the trash particles and fiber fragments flowing behind them, and this greatly diminishes the ability of the device to separate these impurities from the fibers being washed by the air currents. In other words, because of "felting," the fibers just previously washed by air currents become re-contaminated by subsequently arriving impurities, and when the longer desirable fibers are transferred from the purification zone they carry these trapped impurities along with them. For these reasons, and others that will become apparent below, none of the above cited prior art is suitable to meet the objects of the present invention.
Accordingly, it is an object of this invention to provide a fiber length-sorting and purification mechanism that carries fibers on teeth travelling in a first direction while working the fibers under process with a HIGH VELOCITY aero-energy field flowing through the teeth in a generally OPPOSITE direction; so that fibers of a preferred longer length can be held latched to the travelling teeth, while shorter length fibers and other impurities are washed, teased, and stripped (aero-combed) off of the latched longer fibers.
Another object of the present invention is to provide a mechanism that can very efficiently, but gently, strip tightly adhering tiny trash particles and short fibers from longer fibers via a carefully focused high velocity aero-energy field, without incurring the brutal fiber damaging effects associated with sharp edged mote knives.
Another object of the present invention is to provide a mechanism that does not require high centrifugal forces in order to accomplish the fiber length-sorting/purification action.
Another object of the present invention is to provide a fiber length-sorting and purification mechanism that does not require the use of electrostatic forces to restrain the fibers during the length-sorting/purification action itself, because the magnitude of electrostatic forces that can be applied to certain types of fibers, particularly hygroscopic types, such as cotton, are small relative to the tremendous stripping forces needed to separate shorter fibers and small jagged impurities from longer fibers with high efficiency. (It is known that electrostatic forces are most effective in controlling non-conductive fibers that can hold a static electric charge on their surfaces, and hygroscopic fibers readily bleed off static electric charges due to moisture absorption from normal production atmospheres.) It is to be understood, of course, that there are certain embodiments of the present invention where electrostatic forces may be advantageously used to manipulate the fibers (low forces situations) either BEFORE or AFTER the actual length-sorting/purification action occurs in the process.
Another object of the present invention is to provide a fiber length-sorting and purification mechanism that does not depend on the use of a porous defined wall screen, or screens, in order to effect the physical or actual separation of longer desirable fibers from the less desirable components. It is to be understood, of course, that there are embodiments of the present invention where screens may be appropriately used as parts of "condensers" in order to separate a group of fibers from a conveying air stream AFTER the group has been length-sorted/purified, because this is a very practical way to use screens.
These and other objects will become apparent below.